Abstract
High-quality Ta-doped La2Ti2O7 (Ta-LTO) single crystal of about 40 mm in length and 5 mm in diameter was successfully prepared by the optical floating zone method. An X-ray rocking curve reveals that the crystal of LTO has excellent crystalline quality. As-grown crystals were transparent after annealing in air and the transmittance is up to 76% in the visible and near-infrared region. X-ray diffraction showed that this compound possessed a monoclinic structure with P21 space group. The dielectric properties were investigated as functions of temperature (0~300 °C) and frequency (102 Hz~105 Hz). Dielectric spectra indicated an increase in the room-temperature dielectric constant accompanied by a drop in the loss tangent as a result of the Ta doping. One relaxation was observed in the spectra of electric modulus, which was ascribed to be related to the oxygen vacancy. The dielectric relaxation with activation energy of 1.16 eV is found to be the polaron hopping caused by the oxygen vacancies.
Highlights
With the recent progress and development in chemical and material processing, automotive, aerospace, and power-generating industries, there has been an ever-increasing need for actuators and sensors that can be operated at high temperatures [1,2,3]
(a) Ta-La2 Ti2 O7 (LTO) single crystal was annealed for 1 h at 1200 ◦ C; (b) Ta-LTO crystal wafer after annealing; (a) Ta-LTO single crystal was annealed for 1 h at 1200 °C; (b) Ta-LTO crystal wafer after annealing; (c) LTO single crystal by floating zone method (d)
A Ta-doped La2 Ti2 O7 single crystal of about 40 mm in length and 5 mm in diameter was successfully grown by the floating zone method in an argon atmosphere
Summary
With the recent progress and development in chemical and material processing, automotive, aerospace, and power-generating industries, there has been an ever-increasing need for actuators and sensors that can be operated at high temperatures [1,2,3]. It was difficult to prepare a single crystal, since the piezoelectric properties are closely related to the dielectric properties, and in lead zirconate titanate (PZT), pentavalent donor additions (tantalum) were reported to produce significant effects on the mechanical and electrical properties characterized by enhanced dielectric constant and DC resistivity [25]. This motivated us to study effects of tantalum substitution on the structure and dielectric properties of La2 Ti2 O7.
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